Antioxidant or age resister



Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

ALBERT M. CLIFFORD, AKRON, OHIO, ASSIGNOR TO THE GOODYEAR TIRE & RUBBER COMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO.

ANTIO XIDANT OR AGE RESISTER.

No Drawing".

My invention relates to the treatment of rubber and it has particular relation to a novel method of increasing the age-resisting properties of rubber compounds.-

Ill)

' ties. The formula 'ofthis substance may be More specifically, the invention consists in the discovery of a new material which may be incorporated into rubber to enhance'its ability to withstand aging or oxidaton.

Another object of the invention consists in the provision of an'antioxidant or age-retarder that is composed of a 'di-hydroxy diaromatic compound,

Heretofore, it'has been observed that certain plienyl hydroxy and naphthyl hydroxy compounds, when incorporatedinto rubber, act as preservatives or age-retarder thereof. Hydro-quinone and wnaphthol are specific examples of such materials. This invention consists in the discovery that compounds consisting of two hydroxy aromatic molecules attached together in accordancewith the type formula:

Irma-B on,

in which R and R are aromatic groups, may be employed as antioxidants in rubber compounds with excellent result's.

,8di-napthol is a specific example of a compound having the above structure which may be incorporated into rubber compounds to obtaina product having excellent aging qualirepresented as follows:

01,1 Olli One methodof preparing this material consists in the oxidation of ,B-naphthol in an alkaline solution with an acid solution of ferric chloride. These materials are intermixed in the ratio of 83 grams of B-naphthol and grams of sodium hydroxide, dissolved in 3 liters of water. The materials are heated to their boiling point in order to obtain a com plete mixture thereof and are then treated with a solution of 130 grams of ferric chloride dissolved in a solution of 100 grams of hydro- Application filed February 9, 1928. Serial No. 253,221.

be introduced into various rubber compounds with very satisfactory results. The followlng is an example of a compound which insures an excellent product:

Parts. Extracted rubber 100 Zinc oxide 5 Sulphur 3 Stearic acid 1.5 Hexamethylene tetramine 2 Ant-ioxidant 1 Samples of material prepared in accordance with the preceding formula were vulcan ized at a temperature corresponding to 40 pounds steam pressure for periods of 30, and 70 minutes, respectively. One set of these samples was subjected to physical tests to ascertain their elasticity and tensile A yield of 88 to 90% of theoreticalstrength before agin The results of these tests are indicated 'in the following table:

Load in kgs./ c. mJat Cure in Tel-Elle Per cent 40: p s- 2 31 E10? 5007 7 i I 0 i sure Elong, Elong.

50 140 870. is 5 l 185 24 87 I Another set of these samples was subjected to artificial aging in an oxygen bomb for six days ata temperature of 50 C. and a pressure of 50 pounds of oxygen per square inch. These materials were weighed both before and after aging in the bomb, inOrder to ascertain the percentage increase in weight due tothe absorption of oxygen. The samples the preferred Load inkgs/em. at (ll-Ire Per cent Mms. at Tensile Per cent weigh; 403 presstrength Elong. 500,7 7007 more; Sure 0 n r Elong. Elong.

30 105 875 ll .3 50 135 820 20 68 2 70 145 770 2T 98 It will be observed from the tables that the material is an excellent antioxidant, because, to a large extent, it inhibits the absorption of oxygen by the rubber, even when the latter is subjected to the action of-that element at a comparatively high temperature and for a relatively long period of time. Also, it will be observed that exposure to oxygen at a relatively high temperature only" slightly impairs the elasticity and tensile strength of the rubber. Under similar conditions, if the compound had contained no antioxidant, the samples would have been reduced to resinous masses containing twelve percent or more of oxygen andwould be devoid of appreciable elasticity or tensile strength;

Although I have described in detail only embodiments of the invention, it will be apparent to those skilled in the art that it is not so limited but that various minor modifications may be made therein without departing from the spirit of the inclaims.

February, 1928. vention or from the scope of the appended stantially a non-accelerator of the rate of vulcanization.

2. A method of preserving rubber which comprises incorporating therein a di-naphthol.

- 3. A method of preserving rubber which comprises incorporating therein a di-naphthylene having a hydroxyl group substituted therein.

4. A method of preserving rubber whichcomprisesincorporatingtherein a ,G-di-naphthol. 5. A rubber product that has been vulcanized in the presence of a material having the following structural formula:

HOR-R,'OH, in which R and R, are

naphthyl groups, said material being. sub-- stantially a non-accelerator of the rate of vulcanization. I

6. A rubber product that has been vulcanized in the presence of a di-naphthyl radical having at least one hydroxy group attached thereto. i

7 A rubber product that has been vulcanized in the presence of B-di-naphthol.

In witness whereof, I have hereunto signed my name.

Signed at'Akron, in the county of Summit and State of Ohio, U. S. this 8th day of ALBERT M. CLIFFORD. 

